North Carolina Cooperative Extension Service
North Carolina State University

The cereal leaf beetle has become a significant pest of North Carolina
small grains in recent years. Cereal leaf beetle is native to Europe and
was first detected in Michigan in 1962. Since that time it has spread throughout
most of the eastern United States, including most of North Carolina. The
insect can become very numerous in small grain fields and the larva are
capable of reducing grain yield by eating the green leaf tissue.

Cereal Leaf Beetle Description and Life Cycle

Description
-- The adult cereal leaf beetle is about 3/16 inch long and has metallic,
bluish-black head and wing covers. The legs and front segment of the thorax
are rust-red. Eggs are elliptical, about 1/32 of an inch long, and colored
yellow to burnt brownish yellow. Most often the eggs are laid singly or
in small scattered groups on the upper leaf surface between, and aligned
with, the leaf veins. Larva
are very small when newly hatched and grow to a maximum size that is slightly
longer than the adult. Larva are slug-like in shape and resemble small
Colorado potato beetle grubs, except for their coloration. The head and
legs are brownish-black and the body is yellowish. However, body coloration
is usually obscured by a black globule of mucus and fecal matter held on
the body, giving the larva shiny black, wet appearance. This liquid substance
wipes off easily and after walking in an infested field, a person's shoes
and trouser legs will be soiled.

Life Cycle -- Adult cereal leaf beetles overwinter in fallen
leaves, ground litter, or other debris along hedge-rows, within wooded
areas, or other protected sites in the vicinity of last seasons grain fields.
In the spring, adults colonize and lay eggs in small grain fields during
March and April, although it can be earlier or later depending on spring
temperatures. Most egg laying occurs during late March and through mid-April
with adults preferring late-planted and thinly sown fields. Eggs hatch
in about five days. Larvae
develop in about 10-12 days under ideal temperatures, however, development
times vary considerably during the spring. Peak larval populations usually
occur in mid-April to early-May. Small larvae eat a very small amount but
when full grown, larvae have a voracious appetite.

Upon reaching full size, the larvae dig into the ground and pupate.
After a short period in the soil a new summer generation of adult beetles
emerges in late-May and June. New beetles move from small grain fields
and feed on grass plants for a short period but then remain inactive through
most of the summer. Since these adults need to feed before becoming inactive
they often congregate and feed in corn fields adjacent to the small grains
from which they emerged. Adult feeding on corn appears like many line-etchings
on the blades and can cause concern to the farmer. However, damage is usually
cosmetic rather than yield reducing (see section on corn at the end of
this publication). Cereal leaf beetle does not lay eggs in corn. In the
fall, beetles move to wooded areas, hedge-rows, and ditch-banks to overwinter.
There is only one generation per year.

Damage to Small Grains

Damage to wheat, oats, and barley is caused by the larvae feeding on
leaves during April and May. Although adults will feed on young small grains
plants, their feeding does not affect the plant's performance. However,
cereal leaf beetle larvae can reach very high numbers in small grains and
larger larvae can defoliate wheat plants. The larvae eat long strips of
green tissue from between leaf veins and may skeletonize entire leaves,
leaving only the transparent lower leaf surface tissue. Severely defoliated
fields can take on a white "frosted" cast when lots of green
tissue is lost on the upper leaves. Often cereal leaf beetle populations
will be somewhat localized and damage will be confined to spots or sections
of fields or farms.

Damage can build-up quickly, often in as little as five days, after
larvae become large and warm temperatures make the insects very active.
Leaf feeding reduces the plant's ability to make it's food and limits reproductive
growth, particularly if the upper leaves are destroyed. Yield reduction
to 45% has been observed when defoliation was near 100% and the damage
occurred early in the heading period. Later damage, late in the head-fill
period does not have a great impact. Yield reductions of 10% to 20% are
typical in infested commercial fields. Recent research has indicated that
the three stem leaves (flag leaf and two leaves below) all contribute to
filling grain heads and achieving favorable grain test weight. This research
suggests that the flag leaf is about as important as the two stem leaves.
Also, damaged leaves will not be replaced by the plant.

Management of Cereal Leaf Beetle In Small Grains

The North Carolina Department of Agriculture has released several species
of exotic parasites throughout the state. These parasites develop within
cereal leaf beetle eggs and larvae and have the potential to keep populations
below an economic level. Parasite release programs have worked well in
several other states but have had limited success in our state up to the
current time. Efforts are to introduce new and better adapted parasites
for North Carolina are continuing. Native biological control agents, especially
lady beetles, appear to consume cereal leaf beetle eggs and, perhaps, young
larvae in early spring. Whereas farmers can do little to stimulate the
development of these biological control agents, unnecessary or excessively
early insecticide application may cause cereal leaf beetle problems by
removing these valuable predators. Therefore, insecticides should applied
only on the basis of a need as determined by proper scouting and threshold
use. Avoid using insecticide with top dressed nitrogen application as this
has been demonstrated to enhance populations in some cases. Several effective
insecticides are registered for use on small grains (see sections on scouting
and insecticides). In addition, where cereal leaf beetles are present and
the Hessian fly has not been a problem, avoiding late planting may be beneficial.
Late-planted fields are more attractive to cereal leaf beetles for egg
laying in the spring. Additionally, thick planted/tillered wheat fields
are less subject to develop high cereal leaf beetle populations. In general,
following sound agronomic practices for high yield small grain production
reduces the impact of cereal leaf beetle.

Scouting For Cereal Leaf Beetle In Small Grains

Scouting Method -- Scouting should be done after peak egg laying has
occurred and the majority of eggs have hatched, usually in early- to late-April.
Development will occur earlier in the Piedmont vs the Mountains and Coastal
Plain; earlier in south, later in north. On warm springs scouting should
be done earlier than on cooler springs. Scouting should be done when both
eggs and mostly small larvae are in the field (counts should include both
forms). If the population is mainly made-up of eggs, then scouting should
be at a later date, when a minimum of 50% is in the larval stage.

Eggs are elliptical, about 1/32 of an inch long, and colored yellow
to burnt brownish yellow. Most often the eggs are laid singly or in small
scattered groups (often end-on-end)on the upper leaf surface between, and
aligned with, the leaf veins.

Samples should be taken at a minimum of 10 random sites in the interior
of each field (avoid the edges). At each site, 10 tillers (stems) should
be examined for cereal leaf beetle eggs and larvae. This will result in
100 tillers (stems) per field being examined. Eggs may be on the leaves
near the ground. Record the number of eggs and larvae counted at each sample
site. After leaving the field, calculate the total number of eggs + larvae
found. Alternatively, stems can be examined at random while walking through
the major portion of the field; again 100 stems per field should be examined.

Because cereal leaf beetle is often unevenly distributed in the field,
it is necessary to determine if a portion of a field is above threshold.
If the random sampling indicates an uneven distribution (lots in some samples
but few in others), it may be necessary to subdivide the field into two
or more parts and sample each part as an individual field.

In instances of very high counts the sampling can be abbreviated after
the samples have exceeded the threshold. For instance, after examining
30 tillers the scout has found 35 eggs+larva which exceeds the threshold
for 100 stems. However, if this is done the scout should realize that the
portion of the field not scouted may not have high populations.

Threshold for Egg/larval Counts-- 25 eggs and/or larva total per 100
tillers (this is an average of one per each four tillers or 0.25 eggs and/or
larva per tiller)

Scouting Frequency -- Once egg laying has reached a peak, many fields
will need only a single scouting for eggs and larvae. If the proportion
of eggs in the sample is 50% or greater then sample again in 5-7 days.

Insecticidal Control Of Cereal Leaf Beetle In Wheat

The cereal leaf beetle is easily killed with low rates of several insecticides.
When selecting an insecticide for use against cereal leaf beetle, consideration
should be given to the presence of aphids and armyworm since certain insecticides
are better choices for unique pest combinations. Choices are presented
below in Table 1. Cereal leaf beetle has only one generation per year and
if insecticide is applied correctly one application will give adequate
control.

Precautions -- It is not advisable to add an insecticide to top
dress nitrogen. If insecticide is applied very early it will likely fail
to control cereal leaf beetle and can actually increase numbers by removing
predators. Carbaryl (Sevin) formulations, though effective against cereal
leaf beetle, are not suggested for cereal leaf beetle since the insecticide
can stimulate aphid populations in wheat by predator removal and low effectiveness
on aphids. If threshold populations consist of near 50% eggs, Karate insecticide
may be a best choice due to it's longer residual properties. When using
any insecticide always read the lable and follow lable directions.

Table 1. Recommended insecticides for cereal leaf beetle and other
small grains insects which may occur with cereal leaf beetle (amounts/acre)*

PRODUCT*

CEREAL LEAF BTL

ARMYWORM

APHIDS

Malathion 57%

1.5 pt

NO

1.5 pt

Karate 1 EC

2.6 oz

2.6 oz

2.6 oz

Lannate 2.4 LV

1 pt

1 - 1.5 pt

1 pt

Furadan 4F

0.5 pt

NO

NO

*NOTES: All but malathion are restricted use insecticides, use appropriate
precaution. Furadan can not be applied after the grain heads emerge from
the boot. Armyworm and aphid listings are included since they sometimes
occur with cereal leaf beetle or soon thereafter.

Cereal Leaf Beetle In Field Corn

Cereal leaf beetle adults also attack corn foliage. Early spring larvae
build-up in small grains and change to adults in May. Adults emerge as
the small grain crop is drying and migrate to other areas to find suitable
food. Often, corn fields bordering small grain fields are attractive to
the migrating beetles and these adults infest the corn, especially along
the edges nearest small grain. Cereal leaf beetles eat the leaf surface
tissue on whorl stage corn plants. Narrow streaks are eaten between the
leaf veins, usually on the surface but sometimes completely through the
leaf. If beetle populations are very high, defoliation can reduce yield,
but leaf feeding is usually cosmetic. Damage is often alarming to farmers
even if it poses no economic threat. Beetles do not reproduce or remain
for a very long time in corn fields and, therefore, damage is a single,
short-term event that rapidly developing corn plants soon out-grow.

Insecticides are occasionally necessary to prevent serious defoliation
to corn fields or portions of fields. To evaluate the need for treatment,
two factors must be considered: (1) assessing the % defoliation and (2)
determining if beetles are still present in the field at high numbers (is
the defoliation going to get worse?). Corn fields should be scouted for
defoliation (estimate total defoliation on at least 10 plants/field). Defoliation
estimates should be compared to Table 2 to determine potential yield loss.
A 5 bu/acre potential yield loss and a large beetle population will justify
insecticide treatment in most cases. If treatment is necessary, consult
a current edition of the NC Agricultural Chemicals Manual for suggested
insecticides to use in corn. The latest recommendations can be found in
the North Carolina
Agricultural Chemicals Manual.

Recommendations of specific chemicals are based upon information on
the manufacturer's label and performance in a limited number of trials.
Because environmental conditions and methods of application by growers
may vary widely, performance of the chemical will not always conform to
the safety and pest control standards indicated by experimental data.

Recommendations for the use of chemicals are included in this publication
as a convenience to the reader. The use of brand names and any mention
or listing of commercial products or services in this publication does
not imply endorsement by the North Carolina Cooperative Extension Service
nor discrimination against similar products or services not mentioned.
Individuals who use chemicals are responsible for ensuring that the intended
use complies with current regulations and conforms to the product label.
Be sure to obtain current information about usage and examine a current
product label before applying any chemical. For assistance, contact your
county North Carolina Cooperative Extension Service agent.

Other Resources

For assistance with a specific problem, contact your local North
Carolina Cooperative Extension Service personnel.

Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June
30, 1914. Employment and program opportunities are offered to all people
regardless of race, color, national origin, sex, age, or disability. North
Carolina State University at Raleigh, North Carolina A&T State University,
U.S. Department of Agriculture, and local governments cooperating.